Method and apparatus for controlling an internal combustion engine during a combustion transition

Abstract

A method for operating an internal combustion engine includes increasing engine drag torque, transitioning from a cylinder deactivation state to an all-cylinder state, and decreasing engine drag torque immediately subsequent to transitioning to the all-cylinder state.

The invention claimed is: 
     
       1. Method for operating an internal combustion engine, comprising:
 controlling the internal combustion engine in a deceleration fuel cutoff mode and a cylinder deactivation state in response to an operator request for coasting; 
 monitoring an engine operation command; 
 increasing engine drag torque while operating the engine in cylinder deactivation state, comprising closing an engine throttle to a low state, when the monitored engine operation command commands engine operation in an all-cylinder state; 
 transitioning from the cylinder deactivation state to an all-cylinder state while remaining in the deceleration fuel cutoff mode; 
 decreasing engine drag torque directly subsequent to transitioning to the all-cylinder state; and 
 executing an engine autostop. 
 
     
     
       2. The method of  claim 1 , wherein increasing the engine drag torque comprises increasing the engine drag torque to a predetermined level. 
     
     
       3. The method of  claim 1 , wherein increasing engine drag torque further comprises controlling a variable engine valve lift control system to restrict engine airflow. 
     
     
       4. The method of  claim 3 , wherein controlling the variable engine valve lift control system to restrict engine airflow comprises controlling the variable engine valve lift control system to a low-lift engine valve state. 
     
     
       5. The method of  claim 1 , wherein increasing engine drag torque further comprises controlling a variable cam phasing system to restrict engine airflow. 
     
     
       6. The method of  claim 5 , wherein controlling the variable cam phasing system to restrict engine airflow comprises controlling the variable cam phasing system to control cam phasing of the engine to eliminate engine valve overlap. 
     
     
       7. Method for operating a powertrain system, comprising:
 operating the powertrain system in one of a coasting mode and a braking mode, including controlling an internal combustion engine in a deceleration fuel cutoff mode and a cylinder deactivation state and controlling a torque converter clutch in a locked state; and 
 monitoring an engine operation command; 
 increasing engine drag torque while operating the engine in cylinder deactivation state, comprising closing an engine throttle to a low state, when the monitored engine operation command commands engine operation in an all-cylinder state; 
 transitioning from the cylinder deactivation state to an all-cylinder state while controlling the internal combustion engine in the deceleration fuel cutoff mode; 
 decreasing the engine drag torque immediately subsequent to transitioning to the all-cylinder state; 
 unlocking the torque converter clutch; and 
 executing an engine autostop. 
 
     
     
       8. The method of  claim 7 , wherein increasing the engine drag torque comprises increasing the engine drag torque to a predetermined level. 
     
     
       9. The method of  claim 7 , wherein increasing engine drag torque further comprises controlling a variable engine valve lift control system to restrict engine airflow. 
     
     
       10. The method of  claim 7 , wherein increasing engine drag torque further comprises controlling a variable cam phasing system to restrict engine airflow.